The aim of this project is to develop systems for measuring the frequency of point mutations in male germinal tissue. These systems would have the advantage of testing the human population by means of readily available samples, i.e., spermatozoa. At present enzyme histochemical methods are being developed to detect point mutations in male mice. The histochemical staining technique has been quantatized for alpha-glycerophosphate dehydrogenase and succinyl dehydrogenase. Techniques have been developed for selective staining of sperm containing thermo-resistant or urea-resistant alpha-glycerophosphate dehydrogenase. Mutation frequencies have been determined after treatment of the male mice with procarbazine.